1. Field of Invention
This invention relates generally to the treatment of water glass wastewater and more particularly to obtaining alkalophilic/alkaline-tolerant microbes and the use of alkalophilic/alkaline-tolerant microbes cultured on granular activated carbon to directly treat water glass wastewater without any prior pH adjustment and then subsequently recycle water glass from water resource by the different chemical and physical properties of water glass and water.
2. Description of Related Art
The definition of “water glass” is a solution containing colloidal silica particles. Soluble silicates contain three components which all provide some value in consumer applications. Silica is the primary constituent of all soluables silicates. Virtually all of the end-use applications utilize the chemistry of silica. Alkali is also a key component of a soluble silicate. It can be in either a sodium or potassium oxide form and it is responsible for maintaining silica solubility. Water is the third ingredient. While there are anhydrous silicate products available, most contain substantial amounts of water. In almost all cases, water must be added to take advantage of the silica functionality. Sodium silicates or waterglass(Na2O.XSiO2) are metal oxides of silica. All soluble silicates can be differentiated by their ratio, defined as the weight proportion of silica to alkali (SiO2/Na2O). Ratio determines the physical and chemical properties of the product.
Sodium silicate or waterglass(Na2O.XSiO2) is alkaline (pH>11.5). Water glass wastewater is also alkaline (pH usually above 11.0), however, the pH value of the water glass effluent varies according to the water glass concentration of the effluent. Water glass effluent from the textile dyeing industry have pH values as high as 11.5. Once the pH value of water glass effluent is lowered, even with a slight decrease, water glass effluent will coagulate or form solid water glass suspension. In essence, these reactions involve the destabilization of liquid silicate solutions. When the pH value of a liquid silicate is modified to a point below 11, the silica is destabilized and the system polymerizes or gels.
In conventional water glass wastewater treatment, the wastewater is diverted into a neutral biotreatment pond and coagulates or becomes solid water glass suspension, forming inefficacious sludge and purging the effectual biological sludge. Further physical and chemical treatments then lead to the formation of chemical sludge and water glass sludge. The sludge can block the pipes so as to require additional cleaning and removal efforts. Taking the water glass effluent produced by the textile dyeing industry as an example, one ton of water glass wastewater produces 0.3 tons of water glass sludge, which blocks the on-site pipes and gives rise to problems for cleaning and removal of the sludge, severely reducing the efficiency of the on-site activated sludge and chemical treatments.
The sludge formed from conventional water glass wastewater treatment is the cause of the low efficiency in such wastewater processing. Therefore, there is the need for an improved method of water glass wastewater treatment.